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BBC exhaust manifold performance

General engine tech -- Drag Racing to Circle Track

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lucas bremer
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BBC exhaust manifold performance

Post by lucas bremer »

BBC exhuast manifold performance
looking to put manifolds back on my nova
are they going to really kill my car in performance
what can you do to help them
bigjoe1
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Re: BBC exhaust manifold performance

Post by bigjoe1 »

You asked for it=== Way back when I first started dyno testing ( mid 1980 ) On a near stock 396 Chevy BB, It made right at 330 Hp with open headers, no mufflers ( whatever ) The owner of the engine wanted to see what the stock cast iron manifolds would do.. Mind you, the stock Chevelle 396 manifolds with a piece of 2 & 1/2 inch straight pipe , but NO MUFFLER== It LOST 101 horsepower at 5000 RPM== I will NEVER FORGET IT== I do remember when we put a set of headers on my brothers 375 HP 396 Nova, it picked up 1.50 seconds and ten MPH at the dragstrip at a cost of 95 dollars back then for Hooker headers


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Re: BBC exhaust manifold performance

Post by pdq67 »

The old HPBook, "How to HR BB Chevys" tell how just installing a set of headers on a LS-6 454 brought it back up to right at the hp it was advertised to be. Something like I want to say 74 hp over stock 454 manifolds.

Please check it out.

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Re: BBC exhaust manifold performance

Post by lucas bremer »

thanks
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Re: BBC exhaust manifold performance

Post by dfree383 »

To run manifolds you need to run way different cam timing than typical performance stuff thats generally avaliable. You will loose some power, but if its done right it will still make decent numbers and look stock, if thats what your after.
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Re: BBC exhaust manifold performance

Post by novadude »

bigjoe1 wrote:You asked for it=== Way back when I first started dyno testing ( mid 1980 ) On a near stock 396 Chevy BB, It made right at 330 Hp with open headers, no mufflers ( whatever ) The owner of the engine wanted to see what the stock cast iron manifolds would do.. Mind you, the stock Chevelle 396 manifolds with a piece of 2 & 1/2 inch straight pipe , but NO MUFFLER== It LOST 101 horsepower at 5000 RPM== I will NEVER FORGET IT== I do remember when we put a set of headers on my brothers 375 HP 396 Nova, it picked up 1.50 seconds and ten MPH at the dragstrip at a cost of 95 dollars back then for Hooker headers


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Wow! Are you serious? 100 hp loss on a mild 330hp 396? It's a little hard to imagine that 396 manifolds are THAT bad, but I guess dynos do not lie.
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Re: BBC exhaust manifold performance

Post by bigjoe1 »

I wqill tell you this. It was such a shock at the time noone could believe it either..The fact that you could put on a set of headers and pickup a second and a half is pretty radical too== I was there, and I saw it with my own eyes..The BB Nova did have the very worse stock exhaust ever to come from the factory..On my 1970 Chevelle, the headers picked it up about 6 tenths and 6 MPH, but the Chevelle stock exhaust was much better than the BB Nova


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Re: BBC exhaust manifold performance

Post by Keith Morganstein »

novadude wrote:
bigjoe1 wrote:You asked for it=== Way back when I first started dyno testing ( mid 1980 ) On a near stock 396 Chevy BB, It made right at 330 Hp with open headers, no mufflers ( whatever ) The owner of the engine wanted to see what the stock cast iron manifolds would do.. Mind you, the stock Chevelle 396 manifolds with a piece of 2 & 1/2 inch straight pipe , but NO MUFFLER== It LOST 101 horsepower at 5000 RPM== I will NEVER FORGET IT== I do remember when we put a set of headers on my brothers 375 HP 396 Nova, it picked up 1.50 seconds and ten MPH at the dragstrip at a cost of 95 dollars back then for Hooker headers


JOE SHERMAN RACING ENGINES
Wow! Are you serious? 100 hp loss on a mild 330hp 396? It's a little hard to imagine that 396 manifolds are THAT bad, but I guess dynos do not lie.
The Camaro BBC manifolds and similar are very bad.
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Re: BBC exhaust manifold performance

Post by SchmidtMotorWorks »

This raises something I have wondered for a while. With the value of old muscle cars going so high that mostly older people have them now I think many of them would want to ditch the hassles with headers but the performance lost is too much,,what to do?

I wonder if a manifold could be made that would perform better?
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Re: BBC exhaust manifold performance

Post by lucas bremer »

SchmidtMotorWorks wrote:This raises something I have wondered for a while. With the value of old muscle cars going so high that mostly older people have them now I think many of them would want to ditch the hassles with headers but the performance lost is too much,,what to do?

I wonder if a manifold could be made that would perform better?
im not older bay any means but that is were im going!
all out performance is not my goal any more
but high performance is the game!
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Re: BBC exhaust manifold performance

Post by MadBill »

When I started tearing into my brand new '70½ Z-28, I did it in all the wrong order:
1st: Factory cross-ram and 600 VS Holleys. Felt like ~15 HP.
2nd: Factory '140' race cam. Killed the bottom end; added maybe 10 HP at the top.
3rd: Enthusiastic (if not too well-directed) full port job, angle-plug conversion and 0-0.100" angle mill. Substantial gain over the full RPM range, maybe 25 HP at peak.
Finally: 1-¾" Blackjack headers, 3" head pipes into GM Turbo mufflers and 2-½" tailpipes. 100 HP. Really. At least double all the rest combined. #-o
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Re: BBC exhaust manifold performance

Post by novadude »

MadBill wrote:When I started tearing into my brand new '70½ Z-28, I did it in all the wrong order:
1st: Factory cross-ram and 600 VS Holleys. Felt like ~15 HP.
2nd: Factory '140' race cam. Killed the bottom end; added maybe 10 HP at the top.
3rd: Enthusiastic (if not too well-directed) full port job, angle-plug conversion and 0-0.100" angle mill. Substantial gain over the full RPM range, maybe 25 HP at peak.
Finally: 1-¾" Blackjack headers, 3" head pipes into GM Turbo mufflers and 2-½" tailpipes. 100 HP. Really. At least double all the rest combined. #-o
Of course some folks go the other way...

When I had my 5.0 Mustang several years ago, it seemed like all the magazines and internet chatter said that the hot ticket to hp was big aftermarket exhaust. Everyone said that headers, 2.5" pipes, etc would really make the car some alive. I spent a lot of money on quality exhaust parts, hi-flo cats, etc. Was terribly disappointed when the car gained like 0.1 sec and < 1 mph from the changes. Installed a stock lower intake that had the "dogleg" in the front ports opened up (welded on the outside to give enough material to do this), and had general mild clean-up. I think the ported lower intake did more for the car than the exhaust for a LOT less money.

Don't need to get the air out if you can't get it in the engine in the first place! :wink:
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Re: BBC exhaust manifold performance

Post by pdq67 »

Reading is all through the years..

In the big car and 'Vette, the top 396 was rated at 425 hp due to their much bigger/better exhaust manifolds. in the A/F/X cars, it was rated at 375 hp b/c of their tightly tucked in truck-type log shaped exhaust manifolds.

And onna the really old mag issues said that it should have been rated as a true 410hp/396 engine for both exhaust manifold design engines.

I want to say that maybe somebody over at team chevelle said he installed the big car/'Vette cast-iron exhaust manifolds on his car, but it's been a while? I want to say that he had to rework the idler arm and frame a schosh as well as take a bit off the manifolds themselves for needed installation clearance.

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Re: BBC exhaust manifold performance

Post by MrBo »

This must be the manifold ? I could never figure how the 425 hp 396 turned into a 375 hp 396.

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Re: BBC exhaust manifold performance

Post by SchmidtMotorWorks »

There was another manifold in the How to Hot Rod Big Block Chevrolets book that had four outlets, I wonder how that worked out?
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